This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 199 29 471.2, filed on Jun. 26, 1999, the entire disclosure of which is incorporated herein by reference.
The invention relates to a method for producing large scale three-dimensional structural components such as an aircraft fuselage or the like having a barrel-shaped configuration or an oval or circular cross-section.
So-called large volume or jumbo aircraft have fuselages assembled from fuselage wall sections, preferably wall sections reinforced by load supporting elements such as stringers and spars or ribs. One or more plate-shaped floor support grids are mounted inside such large scale fuselages. The floor support grids extend longitudinally inside the fuselage and from one side wall to the opposite side wall.
German Patent Publication DE 34 38 584 A1 discloses an apparatus for the manufacture of an aircraft fuselage, whereby large surface area, curved structural elements are assembled to form fuselage sections. These fuselage sections are then interconnected by an automatically operating orbital riveting machine and by manual labor to form fuselage component sections including slide wall sections and top and bottom wall sections. The riveting takes place along so-called cross-seams, whereby the automatic orbital riveting machine travels along these cross-seams guided by a machine guide rail extending as a ring around the aircraft body or fuselage. The entire orbital riveting machine or system is mounted on a carriage that can travel along or rather in parallel to the longitudinal aircraft axis also referred to as the X-axis.
In the manufacture of aircraft fuselages, it is further known to assemble subassemblies in rigid jigs that determine the geometry of the subassembly. Such rigid jigs operate on the principle of orienting all subassemblies relative to a zero position in a rigid system. According to such a known system, the preassembled subassemblies are deposited in jigs and located relative to fixed system points with a so-called zero alignment. Such a zero alignment system has the disadvantages that the zero alignment can result in deviations, particularly along the interface between individually neighboring subassemblies. Such deviations can fall outside permissible tolerance ranges. Moreover, an adjusting of the individual subassemblies in order to assure the desired overall geometry of the aircraft fuselage is not possible. However, as long as the fuselage has a cylindrical configuration with a circular cross-section, the use of the zero alignment or positioning is possible, whereby the subassemblies forming the lower body half are positioned and riveted first whereupon the cabin floor is inserted and connected with the spars or ribs of the lower body half. A so-called auxiliary carrier, also referred to as a presenting frame, holds the subassembly in position relative to the jig and tool system without any possibility of making compensating adjustments in the positioning. Thus, positional deviations of the floor structure relative to the fuselage body are possible, but cannot be corrected. Once the floor structure and the lower fuselage half are assembled, the upper side wall shell sections and upper shell sections are secured to the lower half, whereby the positioning is again performed by way of the above-mentioned zero alignment.
Efforts have been made for avoiding some of the above described drawbacks. Thus, U.S. Pat. No 5,694,690 (Micale) describes a method for producing large scale aircraft bodies from a plurality of subassemblies, whereby the subassemblies or selected components of the subassemblies are provided with drilled coordination holes for an accurate positioning and assembly of the subassemblies. The coordination holes make sure that the elements of the subassembly are already accurately positioned relative to each other so that the resulting subassemblies become self-locating and thus intrinsically determine the final contour of the aircraft body independently of tooling. The drilling of the coordination holes is accomplished by a computer controlled precision robot which is directed to the drilling locations using a digital data set taken directly from original digital part definition records.
The above described methods leave room for improvement, especially with regard to reducing the assembly costs while still assuring the required accuracy in the configuration of the final large scale product, such as a fuselage for a jumbo aircraft.
In view of the above it is the aim of the invention to achieve the following objects singly or in combination:
to provide an assembly method and apparatus for producing large scale components such as jumbo aircraft bodies, whereby the assembly permits maintaining required, precise tolerance ranges without the need for high precision jigs and without drilling precisely positioned locating holes, while still assuring the, accuracy of the three-dimensional large scale body;
to substantially increase the accessibility of tools to the assembly positions for performing most assembly work by robots, particularly the forming of longitudinal and cross-seams; and
to provide a system and apparatus which substantially is independent of the length of the large scale body so that substantially any required number of subassemblies can be jointed to each other without any additional matching adjustments so that an entire aircraft fuselage can be assembled.
The above objects have been achieved according to the invention by performing the following steps. A prefabricated longitudinal central assembly core is mounted at its ends, for example between support columns. Then, at least one support grid section, such as a floor grid section, is secured to the central assembly core with the aid of clamping tools which mechanically fasten the grid section to the core. Then, shell-shaped body sections such as fuselage top and bottom wall sections and side wall sections, having a defined internal stiffness of their own, are positioned by robot tools which are preferably computer controlled, sequentially around the central assembly core and then mechanically interconnected, for example by riveting. The positioning is performed in such a way that first side wall sections are positioned opposite one another and secured to the support grid section or support grid sections by mechanical tools. Thereafter, bottom wall sections and top wall sections are sequentially secured to the side wall sections and to one another to form individual body sections of a large body such as a fuselage in which the support grid section or support grid sections form a cabin floor support. The fuselage is then completed by interconnecting individual body sections to each other, for example by riveting along cross-seams.
It is an important advantage of the invention that the assembly of the prefabricated wall sections or subsections can take place within a precise tolerance range, whereby, for example an aircraft fuselage section can be assembled with the required precision, yet without jigs or locating holes. All prefabricated subsections, namely the support grid and the wall sections are positioned relative to the prefabricated central assembly core which itself is lightweight and has its own stiffness. The central assembly core forms part of the assembly station and can be reused. The prefabricated fuselage planking, namely the prefabricated wall sections are mounted to the floor support grid or to the floor support grids held in precise positions by the longitudinal central assembly core. By first mounting the side wall sections to the support grid or grids, it becomes possible to mount or assemble the bottom wall section and the top wall section to the side wall sections without any difficulties. In a preferred form, the side wall sections are first secured to the support grid or grids in a row, whereupon the upper and lower or rather the top and bottom wall sections can also be secured in respective rows to the row of side wall sections.
According to a preferred embodiment of the present method, the three-dimensional large structural component is assembled of at least two body sections which are interconnected by the above-mentioned cross-seam, whereby each individual body section is so formed that the lateral or side wall sections are positioned opposite each other and are mechanically connected to the support grid or grids to form a first subsection. Then the respective upper and/or lower shells are mechanically connected to the two side wall sections to form a first body section. Once the first body section is assembled the second body section is assembled in the same manner and further sections are assembled next to the already assembled sections. Each body section is mechanically connected, e.g. by riveting, to the preceding or neighboring body section along the cross-seams.
The method according to the invention is preferably performed by an apparatus that combines the following features. An elongated central assembly core for holding at least one or more support grids is secured with one end to amounting held for example by a column, while the other end of the core is secured to a second mounting. Both mountings hold the core in a precise position relative to the longitudinal axis of a large scale body to be assembled. Tools in the form of movable robots are provided for positioning body shell sections relative to the assembly core and relative to each other. A central processing unit is operatively connected to the tool means for controlling the tool means when they perform a holding, transporting and positioning operation for the assembly of shell sections relative to the floor grid or grids held by the core, whereupon additional tools perform the securing operations.
When the assembly is completed, the large scale body is supported by other supports, the central assembly core is released from the support grid or grids and removed from the body, for example by pulling the core longitudinally out of the body.